[jfengel]

It's not easy to add a heat pump to an existing building. You can't add it to a radiator system. You need to add a whole air handling system.

The heating system in place was good enough. It used existing infrastructure.

Heat pumps are great for new construction, and they're even more important now that you're adding air conditioning. You didn't need air conditioning nearly as much a couple of decades ago.

Heat pumps are very common in US homes. One advantage is that they run off electricity rather than gas, so you don't need to add a gas hookup to the house. Existing European infrastructure is mostly already rigged for gas, so that's not as big an advantage.